1. Field of the Invention
The present invention relates to a sight used as an archery equipment (hereinafter referred to as a “sight”).
2. Related Background Art
As shown in FIG. 1, a bow 1 for use in archery is composed of a bow portion 1 and a string 2. The bow portion 1 is an arcuate plate-like member, to the ends of which the ends of the string 2 are respectively attached. When the string 2 is drawn, the distance between the ends of the bow portion 1 is reduced, and the bow rim is deflected. The deflection of the bow portion 1 causes elastic energy for shooting out an arrow to be accumulated in the bow portion 1. The string 2 transmits the elastic energy accumulated in the bow portion 1 to the arrow.
Further, a stabilizer 3 and a sight 4 are mounted to the bow portion 1 so as to extend forwards from the bow portion 1 respectively. The stabilizer 3 is mounted for the purpose of stabilizing the attitude of the bow and mitigating vibration, impact, etc. The sight 4 is mounted for the purpose of aiming the arrow to the target.
The sight 4 is a device which relates the line of sight of an athlete, the attitude of the bow portion 1 held by the athlete, and the target P. As shown in FIGS. 2A and 2B, the sight 4 has an elevation bar 11, a box 12, and a sight pin 6. The elevation bar 11 is fixed by means of a mounting shaft 5 extending forwards from the bow portion 1 such that the elevation bar 11 is positioned substantially along the vertical direction when shooting is performed with the bow portion 1 upright.
The box 12 is mounted to the elevation bar 11 so as to be slidable along the elevation bar 11. Arranged on the elevation bar 11 is a feed screw 13 elongated in the axial direction of the elevation bar 11. The feed screw 13 is threadedly engaged with the box 12 so that the box 12 can make fine movement along the elevation bar 11 through rotation of the feed screw 13.
The sight pin 6 is mounted to the box 12. The sight pin 6 is formed as a thin and narrow cylinder with a small circular section, and is mounted to the box 12 such that the axis of the pin is substantially aligned with the line connecting the eyes of the athlete and the target P when shooting is performed with the bow portion 1 upright. As shown in FIG. 1, in this condition, the athlete firmly holds the bow portion 1 such that the small circular section of the sight pin 6 is aimed at the target P, whereby it is always possible for the athlete to hold the bow portion 1 in the same condition.
In reality, however, the bow portion 1 cannot always be held perfectly in the same condition in the strict sense. Further, even if the bow portion 1 is held perfectly in the same condition in the strict sense, it can happen that, when the athlete shoots with the sight pin 6 of the sight 4 aimed at the target P, the arrow is off the mark depending upon the physical condition of the athlete, the weather, etc. In such cases, the box 12 is moved along the elevation bar 11 in accordance with the deviation amount to shift the position of the sight pin 6 and correct the previous shooting condition of the athlete. The athlete senses a difference between the shooting the target P with the sight pin 6 at the initial position and the shooting the target P with the position of the sight pin 6 shifted, and thereby can refer to it as information for correction for the next shooting.
In this way, the sight 4, which is a device used as a reference for the athlete when performing shooting next, is required to always exhibit highly accurate positional reproducibility. In particular, due to vibration or the like caused by the deformation of the bow portion 1, the box 12 is likely to be displaced with respect to the elevation bar 11. However, in the conventional sight 4, in which the box 12 is caused to slide along the elevation bar 11, it is necessary to perform dimensional processing on the box 12 and the elevation bar 11, with a gap for processing being maintained between the box 12 and the elevator bar 11. Further, in this processing, a dimensional tolerance is naturally required. As a result, between the box 12 and the elevation bar 11, in each dimension, there exists a gap caused by a tolerance required. This gap leads to rattling of the box 12 with respect to the elevation bar 11, and by extension, to a positional error of the box 12 with respect to the elevation bar 11. Such rattling is generated in both the horizontal and the vertical directions of the sections of the box 12 and the elevation bar 11. That is, though needed in terms of processing, this gap leads to rather poor reproduction performance for an archery-sight, resulting in rather poor usability for the athlete.